DE19745921A1 - Polyester molding composition useful for blow molding - Google Patents

Abstract

A thermoplastic polyester molding composition (I) comprises (A) 80-100 wt.% of a polyalkylene arylate having a crystallization exotherm width at half height of no more than 5 deg C and (B) 0-20 wt.% further additives. Independent claims are included for (i) optical fiber sheathing and cable sheathing prepared from (I) and (ii) a process for the production of (I) by (a) esterification and/or ester exchange of an aromatic dicarboxylic acid, ester and/or ester forming derivative with a molar excess of a dihydroxy compound; (b) precondensing the resulting product followed by (c) polycondensation to a viscosity number of 158 ml/g whereby (a) and (b) are carried out in at least 2 temperature zones and optionally adding (B) before cooling of the melt before or after step (c).

Description

The invention relates to the use of thermoplastic polyester molding compositions containing

• A) 80 to 100 wt .-% of a polyalkylene arylate with a half value range of the crystallization isotherms of ≦ 5 ° C
• B) 0 to 20% by weight of further additives,
  the weight percentages of components A) and B) being 100%,
  for the production of moldings by blow molding, profile extrusion and / or pipe extrusion.

The invention further relates to processes for producing the Molding compositions which can be used according to the invention and which are obtained here shaped body.

Polyester are characterized by a low water absorption and good dimensional stability and solvent resistance.

Mixtures of polyesters with other additives have been around known for a long time. The known polyester can only be thing to process blow moldings. Blow molding is common my extruded a tube of polymer melt that between the two half shells of the opened tool hangs. Then The tool is closed and the polymer tube is closed Internal gas pressure is pressed against the tool, cooled and removed forms.

An essential prerequisite for this processing is that the Polymer tubing when extruding in the periods where it is free hangs between the tools, does not tear off, so that the For process can be completed. It is desirable in addition, that the hose does not "sag" because this thin walls in the upper half and thicker walls arise in the lower half. Hollow body with different Wall thicknesses are not suitable for use because the resilience usually from the point with the smallest wall thickness is limited. The molding compositions known from the prior art  can therefore only be used to a very limited extent for the blow molding process use because the hose strength is too low.

Usually high molecular weight polyesters were used for blow molding set which are produced discontinuously z. B. by Polycondensation and subsequent solid phase post-condensation such as for example in DD-A 138074, DE-A 30 12 692 and DE-A 30 22 076 described.

Long residence times and a disadvantage of these processes unwanted yellowing of the resulting polyester by ther mix load.

The assembly of high molecular polyester with other additives substances that, depending on the type and quantity, the desired properties and affect the processing of the polyester, but is not possible, because a molecular weight reduction occurs during assembly occurs so that - even when using high molecular weight output polymers - masses unsuitable for blow molding in any case stand.

The use of polyesters, especially polybutylene terephthalate (PBT) for the production of fiber optic jackets lungs is for example from DD-A 258 859, DE-A 43 03 116, DE-A 42 12 146, DE-A 42 19 607, DE-A 41 42 047 and EP-A 336 806 known.

According to JP-A 08/227 030 has a for wrapping optical Lei Suitable PBT has an intrinsic viscosity of 1.2, one Carboxyl end group content of 40 meq / kg PBT and nucleation medium, phosphorus compounds and sterically hindered phenols as Stabilizers on. The difference from melting point to crystal Initialization temperature should be <30.

JP-A 08/146 261 describes for the improvement of the user´s own add polycarbonate and stabilizers to poly esters.

The polyesters known from the prior art are only suitable required for so-called extrusion applications, especially for light waveguide (FO) coverings.

This is due to the substance z. B. PBT has a moderate characterized crystallization tendency. On the other hand there are the special ones Process conditions in the manufacture of fiber optics add to the difficulty. The Production takes place in the extrusion process using a crosshead (similar to cable sheathing), often with a cold water bath  and also cold gel (inner filling of the tubes) is worked; of the high take-off speeds also practice an additional one deterrent or hypothermic effect. The approximately 260-270 ° C hot melt hose is expelled immediately after it emerges the crosshead (mm or a few cm) a cold gel or something exposed.

If the polyester does not crystallize sufficiently well hypothermia in this critical area the melt. This will ensure adequate crystallization suppresses the melt (and thus its solidification) so far, that the extrudate from the downstream equipment (deduction, etc.) an oval cross section is deformed.

Another consequence of a low tendency to crystallize are for example poor mechanical properties, low di dimensional stability and insufficient resistance to hydrolysis (last teres is also due to the amount of carboxyl end groups certainly).

The following have on the functionality of the optical fibers Parameters of the extrudate significant influence.

Extrudate surface

Rough uneven surfaces (on the inside) lead to one Increase in the attenuation of the glass fibers and thus a leg transmission quality. A length is required difference of the main cross-sectional axes of 0.05 mm, accordingly <2% of the outside diameter.

Roundness

Inadmissible deviations in the roundness lead to so-called Stranded structures that are no longer symmetrical and therefore the Limit the capacity of a cable bundle.

Resistant to hydrolysis

The pipe material must be sufficiently resistant to water or damp atmosphere, so that even after a long time a problem loose assembly without risk of breakage is possible. The shrinking should be <1%.

After shrinking

If the shrinkage is too high, the pipe cross-section narrows, see above that the glass threads have less space, the damping increases and the transmission quality suffers.

The present invention was based on the object, high molecular weight There are readily crystallizing polyester molding compounds available who are continuously and regardless of the type of Feed materials easily to blow molded articles, profile extrudates or have pipe extrudates processed.

The moldings should have good surfaces and good dimensional stability quality (caliber accuracy), hydrolysis resistance and a ge rings shrink.

According to the invention, this object is achieved through the use of poly ester molding compositions according to claim 1 solved. Preferred execution shapes and methods of manufacture are to the subclaims remove.

The usable compounds according to the invention contain as component (A) Molding compositions 80 to 100, preferably 90 to 100, 50 to 85% by weight a thermoplastic polyalkylene arylate.

Generally, polyesters are based on aromatic dicarbon acids and an aliphatic dihydroxy compound used.

A first group of preferred polyesters are polyalkylene tereph thalates with 2 to 10 carbon atoms in the alcohol part.

Such polyalkylene terephthalates are known per se and are described in the literature. They contain an aromatic ring in the main chain, which comes from the aromatic dicarboxylic acid. The aromatic ring can also be substituted, e.g. B. by Ha logen such as chlorine and bromine or by C ₁ -C ₄ alkyl groups such as methyl, ethyl, i- or n-propyl and n-, i- or t-butyl groups.

These polyalkylene terephthalates can by aroma reaction tables dicarboxylic acids, their esters or other ester-forming Derivatives with aliphatic dihydroxy compounds in themselves known way.

The preferred dicarboxylic acids are 2,6-naphthalenedicarboxylic acid and terephthalic acid or mixtures thereof. Up to 30 mol%, preferably not more than 10 mol% of the aromatic Dicarboxylic acids can be aliphatic or cycloaliphatic  Dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dode candic acids and cyclohexanedicarboxylic acids are replaced.

Of the aliphatic dihydroxy compounds, diols with 2 up to 6 carbon atoms, in particular 1,2-ethanediol, 1,3-propane diol, 1,4-butanediol, 1,6-hexanediol, 1,4-hexanediol, 1,4-cyclo hexanediol, 1,4-cyclohexanedimethylanol and neopentyl glycol or their mixtures preferred.

Polyalkylene tereph are particularly preferred polyesters (A) thalates derived from alkane diols with 2 to 6 carbon atoms, to call. Of these, polyethylene terephthalate in particular and polybutylene terephthalate or mixtures thereof are preferred.

Polyesters and their carboxyl end groups are particularly preferred content up to 50 meq / kg, preferably up to 30 meq / kg and ins special up to 27 meq / kg polyester. Such polyester can, for example, based on the method of DE-A 44 01 055 can be produced. The carboxyl end group content is usually determined by titration methods (e.g. potentioms trie) determined.

The viscosity number of the polyester (A) after the continuous orier melt condensation at least 158 ml / g, preferably 168 ml / g and in particular at least 170 ml / g, measured in one 0.5% by weight solution in a phenol / o-dichloro mixture (weight ratio 1: 1) at 25 ° C (according to DIN 53728).

Under the half-value range of crystallization exotherms generally their width (in ° C) at half height. The Kri Installation exotherm is carried out by DSC (differential scanning approx lonimetry) measurements at cooling and heating rates of 20 ° C / min averages.

The full width at half maximum should be ≦ 5 ° C, preferably 4.5 and ins particularly betragen 4 ° C.

Component B) which can be used according to the invention thermoplastic molding compounds other additives and processing aids such as stabilizers, antioxidants, agents against heat decomposition and decomposition by ultraviolet light, Lubricants and mold release agents, colorants such as dyes and pig elements, powdered fillers and reinforcing agents, nucleation medium, plasticizers, etc., their proportion usually not more than 20% by weight, preferably not more than 10% by weight wearing.  

As examples of oxidation retarders and heat stabilizers are sterically hindered phenols, hydroquinones, aromatic se customary amines such as diphenylamines, various substituted ver treads of these groups and their mixtures in concentrations up to 1% by weight, based on the weight of the thermoplastic mold called masses.

As UV stabilizers, generally in amounts up to 2% by weight, based on the molding composition, are used various substituted resorcinols, salicylates, benzotriazoles and Called benzophenones.

Organic dyes such as nigrosine, pigments such as Titanium dioxide, cadmium sulfide, cadmium selenide, phthalocyanines, Ul tramarine blue and carbon black are added as colorants, as well powdered fillers and reinforcing agents. examples for the latter are minerals, amorphous silica, asbestos, calcium si licat (wollastonite), aluminum silicate, magnesium carbonate, kaolin, Chalk, powdered quartz, mica and feldspar. The share of like fillers and dyes is generally up to 20% by weight, preferably up to 10% by weight and in particular up to 5% by weight.

Sodium phenylphosphinate, aluminum can be used as nucleating agents oxide, silicon dioxide, nylon 22 and preferably talc become.

Lubricants and mold release agents, which are usually in amounts up to 1% by weight are preferably long-chain fat acids (e.g. stearic acid or behenic acid), their salts (e.g. Ca or Zn stearate) or ester derivatives (e.g. stearyl stearate or Pentaerythritol tetrastearate) and amide derivatives (e.g. ethylene bis stearylamide), which is preferably mixed with 1,6-hexanediol be used.

Examples of plasticizers are phthalic acid dioctyl ester, Phthalic acid dibenzyl ester, phthalic acid butyl benzyl ester, coals hydrogen oils, N- (n-butyl) benzenesulfonamide and o- and p-tolyls called thylsulfonamide.

The molding compositions according to the invention can still contain 0 to 2% by weight contain fluorine-containing ethylene polymers. This is what it is about are polymers of ethylene with a fluorine content of 55 to 76% by weight, preferably 70 to 76% by weight.  

Examples include polytetrafluoroethylene (PTFE), tetra fluoroethylene-hexafluoroethylene copolymers or tetrafluoroethylene Copolymers with smaller proportions (usually up to 50% by weight) of copolymerizable ethylenically unsaturated monomers rer. These are e.g. B. from Schildknecht in "Vinyl and Related Polymers ", Wiley-Verlag, 1952, pages 484 to 494 and von Wall in "Fluoropolymers" (Wiley interscience, 1972).

These fluorine-containing ethylene polymers are homogeneously distributed in the molding compositions and preferably have a particle size d ₅₀ (number average) in the range from 0.05 to 10 μm, in particular from 0.1 to 5 μm. These small particle sizes can be achieved particularly preferably by using aqueous dispersions of fluorine-containing ethylene polymers and incorporating them into a polyester melt.

For better compatibility with the thermoplastic polyester are minerals and fillers with an adhesive if necessary medium equipped. Glycidyl, vinyl and amino are preferred alkyltrialkoxysilanes.

Polycarbodiimides (PCDI) may be mentioned as preferred additives for improving the surface, in particular those of the general formula:

in the
R is identical or different and is selected from the group of -NCO-, -NHCONHR ¹ -, -NHCONR ¹ R ² - and -NHCOOR ³ radicals, where
R ¹ and R ^{2 are the} same or different and are an alkyl, cyclo alkyl or aralkyl radical and
R ³ is R ¹ or an alkoxypolyoxyalkylene radical and
n is an integer from 0 to 10.

Such PCDI's and processes for their production are u. a. WO-A 96/17011. The PCDI's are in a lot up to 3, preferably up to 2% by weight in the polyester molding compositions contain.

The polyester molding compositions which can be used according to the invention are produced continuously by:

• a) in a first stage an aromatic dicarboxylic acid or their esters or ester-forming derivatives with a molar Excess of a dihydroxy compound esterified or transesterified,
• b) in a second stage that obtained in a) Pre-condensed transesterification or esterification product and
• c) in a third stage, the product obtainable from b) a VZ of at least 158 ml / g polycondensed, where stage a) and stage b) of the process in at least performs two temperature zones and before or after the poly condensation c) optionally adding component (s) B.

Stage a) of the process is called a so-called transesterification or Esterification reaction called. This will be in at least two, preferably carried out at least three temperature zones. The Temperature of the following zone should be 1-40, preferably 2-30 and especially 5-10 ° C higher than the temperature of the previous towards the zone. The temperature range for the entire esterification The reaction is generally 165 (depending on the starting material) to 260, preferably 170 to 250 and in particular 180 to 240 ° C, the pressure is generally from 1 to 10, preferably from 1 to 4 and in particular from 1 to 2 bar.

Step a) of the process is preferably carried out in such a way that one in at least two temperature zones at largely the same Pressure conditions in the individual zones. The techni requirements such as equipment (e.g. in the form of a boiler cascades) to create different temperature zones are known to the expert, which is why further details do not need to do this.

The feedstocks such as diols and acids have already been mentioned above (Component A) described.  

A molar excess of is usually used for the reaction Diol used to balance the ester in the desired Affect shape. The molar ratios of dicarboxylic acid or Dicarboxylic acid esters: Diol are usually 1: 1.1 to 1: 3.5 preferably 1: 1.2 to 1: 2.2. Mol are very particularly preferred Ratios of dicarboxylic acid: diol from 1: 1.5 to 1: 2, as well Diester: diol from 1: 1.25 to 1.5.

However, it is also possible with a smaller excess of diol to carry out the ester reaction in the first zone and correspond Add further amounts of diol in the other temperature zones ben. In the preferred embodiment of the invention Process with three temperature zones, the entire diol is in 3 zones divided as follows: 60 to 85 (1), 10 to 25 (2) and 5-15 (3), preferably: 70 to 80 (1), 10 to 20 (2), 5 to 10 (3).

The dwell times for the entire stage a) are 140 to 300, preferably from 150 to 260 and in particular from 160 to 220 min., The dwell time for the first zone is from 100 to 190, preferably from 110 to 150; for the second zone from 65 to 140, preferably from 65 to 110 minutes. For the preferred off with 3 zones, the dwell time in the 3rd zone is 15 to 45, preferably 15 to 30, minutes, the residence time Reduce accordingly in the 2nd zone and in the 1st zone as above can be maintained.

In the preferred embodiment of the method according to the invention rens take the dwell times from the first zone to the third Zone in a ratio of preferably 6: 3: 1.

Before stage a) of the process, one is particularly preferred th embodiment of the dihydroxy compound first a catalyze sator and then an (earth) alkali metal compound puts.

Preferred catalysts are titanium compounds and tin connections like u. a. from US 39 36 421, US 43 29 444 Pa are known. Preferred connections are Tetrabutyl orthotitanate and triisopropyl titanate and tin di-oc called toat, which is usually in step a) in amounts of 20 to 150, preferably 20 to 120 and in particular 30 up to 70 ppm (based on the metal) can be used.

To further reduce the carboxyl end group content of the poly esters it may be advantageous before implementing the output monomeric 0.1 to 10 mmol, preferably 0.2 to 0.65 mmol, per kg  Polyester, an alkali metal compound or alkaline earth metal ver binding (calculated as alkali metal or alkaline earth metal) ben. Such compounds are featured in DE-A 43 33 930 beat. The preferred compounds are sodium carbonate, Sodium acetate, and sodium alcoholates, especially sodium called methanolate.

The transesterification or esterification products are then in the precondensation stage b) transferred continuously.

This has at least two, preferably at least three and in particular at least four temperature zones. The temperature the following zone is 1 to 40, preferably 2-30 and especially 5-20 ° C higher than the temperature of the previous zone. The temperature range for the entire precondensation is general (depending on the starting materials) at 220 to 300, preferably as at 225 to 290 and especially at 240 to 290 ° C.

Pre-condensation is preferably carried out in such a way that first zone the pressure 0.5 to 1 bar, preferably 0.6 to 0.8 bar is and in the second or last zone 20 to 200, preferably is 25 to 150 mbar and in particular 50 to 150 mbar. Technically, z. B. a vertical tube bundle reactor are used, other reactors are to be carried out known to the expert.

The residence times for the entire stage b) are Process from 10 to 80, preferably from 15 to 50 and especially from 20 to 40 min.

In a particularly preferred embodiment of the invention According to the method, four temperature zones are used, whereby from zone to zone the temperature in the ver conditions increases and the pressure from the first to the fourth Zone is reduced within the limits described. The fourth zone is in this preferred embodiment of the Tube bundle heat exchanger from a device for separating Vapor and liquid phase (also known as vapor separation vessels), where the ratio of the volume of the separation vessel to the volume in the tubes preferably 5 to 15: 1, in particular 8 to 13: 1 be wearing.

The volume ratios of the first three zones are designed in this particularly preferred embodiment so that the first zone from 30 to 60, preferably 50%, the second zone from 20 to 40, preferably 30% and the third zone from 10 to 30, before preferably make up 20% of the volume (volume ratios). The temperature ranges, pressure ranges and residence times for the particularly preferred embodiment of the process according to the invention are listed below:

• 1. Zone: temperature from 230 to 270, preferably from 240 to 250 ° C, pressure from 0.6 to 0.9, preferably from 0.7 to 0.9 bar.
  Residence time from 10 to 30, preferably from 15 to 25, minutes.
• 2nd zone: temperature from 240 to 280, preferably from 250 to 270 ° C, pressure from 0.2 to 0.6, preferably from 0.3 to 0.5 bar.
  Residence time from 5 to 25, preferably from 7 to 15 minutes.
• 3rd zone: temperature from 245 to 290, preferably from 250 to 280 ° C., pressure from 0.1 to 0.3, preferably from 0.1 to 0.25 bar.
  Residence time from 5 to 10, preferably from 4 to 8 minutes.
• 4th zone: temperature from 250 to 300, preferably from 252 to 285 ° C., pressure from 0.015 to 0.2, preferably from 0.025 to 0.15 bar.
  Residence time from 10 to 30, preferably from 14 to 24, minutes.

Those mentioned above in step a) of the process Catalysts and other additives can be mentioned in the Quantities are added in step b) of the process.

After stage b) of the process according to the invention, this Polyester prepolymer has a viscosity number of 15 to 50, preferably have from 20 to 30 ml / g, measured as 0.5 wt .-% solution in Phenol / o-dichlorobenzene (1: 1) according to DIN 53728, part 3 (1985) 25 ° C.

The polyester prepolymer is then in step c) of transferred method according to the invention. This is preferred carried out in one stage at temperatures of 240 to 290, preferably example from 240 to 270 and in particular 240 to 265 ° C. The pressure is from 0.3 to 10, preferably 0.3 to 5 and in particular 0.3 to 2 mbar.

The residence times are usually 30 to 180, preferably  from 35 to 150 min.

During the polycondensation, a surface may preferably be used Renew the product. Surface renewal be indicates that new polymer is constantly appearing on the surface of the Melt arrives so that the exit of the diol is facilitated.

This is preferably 1 to 20 and in particular 1.5 to 6 m ² / kg of product and minute.

It can also be an advantage at this stage of Ver driving catalysts and other additives as they add have been described above.

The product is then ent by means of conventional devices discharged as a strand, cooled and processed into granules.

After the continuous polycondensation, the polyester shows a viscosity number of at least 158, preferably of 168 ml / g, determined in a 0.5 wt .-% solution in one Phenol / o-dichlorobenzene mixture (weight ratio 1: 1 at 25 ° C) according to DIN 53728, 3rd part (1985).

Those obtainable according to the method described above high molecular polyesters show a high crystallization rate supply.

Therefore, they are suitable for the production of blow molded articles, Profile and pipe extrudates of all kinds, especially for cables claddings and fiber optic claddings. The moldings white good mechanical properties, good dimensional stability and hydrolysis resistance in addition to a good surface and low shrinkage.

Examples example 1 Stage a)

881.8 g of dimethyl terephthalate (DMT) and 563.7 g of 1,4-butanediol (BD) were fed into a stirred reactor in a continuous manner. Before contacting the DMT, 781.8 mg of tetrabutyl orthotitanite and 99 micro1 of a 30% by weight solution of NaOCH ₃ in methanol were continuously mixed into the butanediol.

The temperature in the first reaction zone was 185 ° C. at one Pressure of 1 bar and an average residence time of 184 min.

The temperature in the second reaction zone was 205 ° C. at one Pressure of 1 bar and an average residence time of 65 min.

The temperature in the third reaction zone was 210 ° C at one Pressure of 1 bar and an average residence time of 41 min.

The resulting distillates were in a column system separated, with DMT and BD being returned to the reaction.

Stage b)

With a conversion of 94%, the transesterification product was a sen vertical pipe fed, which is divided into 4 heating zones was.

The temperature in the first reaction zone was 245 ° C. at one Pressure of 700 mbar and an average residence time of 22 min.

The temperature in the second reaction zone was 250 ° C. at one Pressure of 400 mbar and an average residence time of 12 min.

The temperature in the third reaction zone was 255 ° C. at one Pressure of 150 mbar and an average residence time of 6 min.

The temperature in the fourth reaction zone was 255 ° C. at one Pressure of 50 mbar and an average residence time of 18 min.

The excess BD and the reaction products such as THF and water were separated at the top of the reaction tube and gear works.

Stage c)

The precondensate was in without further addition of catalysts transferred to a polycondensation reactor.

The temperature in the reaction zone was 255 ° C at one pressure of 0.5 mbar and an average residence time of 115 min.

The product obtained had a VZ of 164 ml / g and one Carboxyl end group content (CEG) of 23 meq / kg, a yellowness index of ΔB 1.9 against white standard and a half-width of the crystals lization exotherm of 3.1 ° C.  

Example 2

The example was carried out analogously to example 1, but with a temperature in stage c) of 257 ° C. at a pressure of 0.5 mbar and an average residence time of 130 min and a surface renewal of 4 m ² / h. kg PBT. A product with a VZ of 169 ml / g and a CEG of 20 meq / kg, a yellowness index of ΔB 2.3 against the white standard and a half-value range of the crystallization exotherm of 3.1 ° C. was obtained.

Example 3

The example was carried out analogously to example 1, but with a temperature in stage c) of 257 ° C. at a pressure of 0.5 mbar and an average residence time of 140 min and a surface renewal of 6.2 m ² / h. kg PBT. A product with a VZ of 187 ml / g and a CEG of 23 meq / kg, a yellowness index of ΔB 2.5 against a white standard and a half-value range of the crystallization exotherm of 3.4 ° C. was obtained.

Example 4

The experiment was carried out as described in Example 1; the melt after the final reactor but before cooling 0.5% by weight of a stearate of pentaerythritol was admixed.

The product obtained had a VN of 167 ml / g and a CEG of 24 meq / kg, a yellowness index of ΔB 2 against white standard and a half-width of the crystallization exotherm of 3.3 ° C.

Comparative Example A

The experiment was carried out as described in Example 1; the temperature being 265 ° C and the residence time 145 min Step c) was.

The product obtained had a VZ of 142 ml / g and a CEG of 31 meq / kg, a yellowness index of ΔB 2.0 against the white standard.

The product was subsequently condensed at 205 ° C. under N ₂ flow in the solid phase.

The product obtained after the solid phase condensation had one VZ of 160 ml / g a CEG of 39 meq / kg, a yellowness index of ΔB 3.8 against white standard and a half-width of the crystallisa tion exotherm at 8.7 ° C.  

Comparative Example B

The experiment was carried out as described in Example 1; the temperature in step c) 255 ° C at a pressure of 0.8 mbar and an average residence time of 105 min.

The product obtained had a VZ of 124 ml / g and a CEG of 24 meq / kg. The product was condensed at 205 ° C. under a stream of N _{2 to a} VN of 176 ml / g. The product obtained after the solid-phase condensation had a CEG of 19 meq / kg, a yellowness index of ΔB 3.2 against the white standard and a half-value range of the crystallization exotherm of 6.1 ° C.

The VZ was at 25 ° C on a 0.5% solution of the polymer in one 1: 1 mixture of phenol / o-dichlorobenzene measured.

The crystallization was carried out by means of DSC after a single melting zen up to 250 ° C with a cooling rate of 20 ° C / min measured. The half value width was determined as the width of the crystallization peak (in ° C) measured halfway between the baseline and the peak maximum.

The carboxyl end groups (CEG) were determined by potentiometric Titra tion of the Po when reacting a sample dissolved in nitrobenzene free with a defined excess of potassium acetate set acetic acid determined.

The yellowness index ΔB was determined according to DIN 5033 part 6 against a whitening stone dard determined.

Processing to extrudate

The from Examples 1 to 4 and Comparative Examples A and B were obtained on a for the production of Optical fiber cables usual system, e.g. B. a 45 mm one shaft extruder from Nokia-Maillefer for hollow tubes with one Extruded inside and an outside diameter of 1.9 and 2.5 mm.

The melt temperature was 260 ° C.

The maximum possible take-off speed as a measure of the quality of the product for the extrusion application is shown in the table forth.  

The processing and product parameters assessed were assessed as follows:
Roundness: measure of the ovality of the pipe cross-section.

Post-shrinking: decrease in length when storing untensioned Pipe sections at 70 ° C for 3 min.

The hydrolysis stability was enhanced by storing extrudates a temperature of 85 ° C and a relative humidity of 85% determined over a period of 60 days.

The hydrolysis test is considered passed if the most stored VZ measured extrudate still has a minimum value of <70 ml / g.

The results of the measurements can be found in the table.  

Claims (11)

1. Use of thermoplastic polyester molding compositions, containing tend

• A) 80 to 100 wt .-% of a polyalkylene arylate with a half-value range of crystallization exotherms of ≧ 5 ° C.
• B) 0 to 20% by weight of further additives,
  the weight percentages of components A) and B) being 100%,
  for the production of molded articles by blow molding, profile extrusion and / or pipe extrusion.

2. Use according to claim 1, in which component A) Carboxyl end group content of ≧ 30 meq / kg. 3. A process for the preparation of the molding compositions which can be used according to claim 1 or 2, characterized in that

• a) in a first stage, an aromatic dicarboxylic acid or its ester or ester-forming derivative is esterified or transesterified with a molar excess of a dihydroxy compound,
• b) in a second stage, the transesterification or esterification product obtained according to a) is precondensed and
• c) in a third stage, the product obtainable from b) is polycondensed to a VZ of at least 158 ml / g,
  wherein stages a) and b) of the process are carried out in at least two temperature zones and component B) is optionally added before or after the poly condensation c) before the melt is cooled.

4. The method according to claim 3, characterized in that one the dihydroxy compound before step a) first with a Catalyst and then with an (earth) alkali compound transferred.   5. The method according to claim 4, characterized in that one the (earth) alkali compound in amounts of 0.1 to 10 mmol calculates as (earth) alkali metal per kg of polyester. 6. The method according to claims 3 to 5, characterized in net that stage a) and / or b) of the process in min carries out at least 3 temperature zones. 7. The method according to claims 3 to 6, characterized in net that the temperature in stage a) and / or b) of the fol Zone 1 to 40 ° C higher than the temperature of the previous zone. 8. The method according to claims 3 to 7, characterized in net that the stage a) under largely the same pressure conditions and stage b) under decreasing pressure ratio nits. 9. The method according to claims 3 to 8, characterized in net that you step c) at a pressure below 2 mbar. 10. Blow molded articles, profile extrudates, pipe extrudates available from the molding compositions usable according to claims 1 or 2 as obtainable according to the procedural conditions of the claims che 3 to 9. 11. Cable sheathing, fiber optic sheathing, receives Lich from the form usable according to claims 1 or 2 masses and available according to the process conditions of Claims 3 to 9.